Investigation on the effectiveness of the repair method 8.3 “Corrosion protection by increasing the electrical resistivity” in chloride-containing concrete Part 2: Chloride redistribution in concrete after application of a system sealing surface protective coating

This DFG-funded research project aimed to gain a better understanding of the mechanisms of the W-Cl repair principle within the framework of fundamental investigations, to contribute to the creation of the necessary basis for a broader application of the repair principle in practice. The focus was on the development of a model to describe the chloride redistribution after the application of a system sealing surface protective coating. On the basis of Fick's second law of diffusion, a mathematical model with a self-contained analytical solution was developed, with the help of which the chloride redistribution after application of a system sealing surface protective coating can be calculated under the idealized assumption of complete water saturation of the concrete. Furthermore, the influence of the dehydration of the concrete, expected as a result of the application of the repair principle W-Cl, on the chloride redistribution was investigated. On the basis of laboratory tests and numerical simulations, material-specific reduction functions were developed to quantify the relationship between the chloride diffusion coefficient and the ambient humidity.     

KINETICS FOR LOW TEMPERATURE PYROLYSIS OF BLACK LIQUOR

A kinetic study of pyrolysis of dried black liquor was performed using a Netzsch 429 Thermogravimetric Analyzer. It was found that as conversion increases from 10 to 45% the apparent pyrolysis activation energy for black liquor increases from 77.20 to 112.74 KJ/mol. For black liquor the order of reaction was found to be first-order. The reaction rate constant was found to be 2.12×10⁹ min. These results are in agreement with the data reported by other investigators on biomass pyrolysis.     

Excavation and support design of the Dicle–Kralkizi water tunnel: an overview

Tunneling projects have their uniqueness in terms of engineering problems. The expertise gained from analyzing these projects establishes a sound basis for future application. This paper conveys experiences gained during the construction and support of the design of the Dicle–Kralkizi water tunnel, Turkey. Tunnel stability problems including overbreaks and surface subsidence are evaluated. An analysis of the breakdowns, factors controlling advance rate and the overall performance of tunnel are covered. The accumulated information presented here is believed to be useful and reliable for a successful tunnel excavation in similar formations.     

Effects of dowels produced from various materials on withdrawal strength in MDF and Pb

Wood dowels are commonly used in the construction furniture, but little information is available about the additive effects of dowels on the ultimate withdrawal strength of single or multidowel joints. This study was carried out to determine the tensile strength of 10‐mm‐diameter dowels produced from medium‐density fiberboard (MDF), plywood, scotch pine (Pinus sylvestris L.), and beech (Fagus orientalis lipsky), bonded parallel and vertical to the surface of MDF and particleboard (Pb) with poly(vinyl acetate) (PVAc) and Desmodur‐VTKA (D‐VTKA). Tensile strength was applied to the dowels according to the procedure in the ASTM‐D 1037 standard. The effects of dowel species, direction of tensile, composite material, and type of adhesive on tensile strength were determined. The results showed that the highest tensile strength was obtained in beech dowels bonded vertically with PVAc adhesive to the surface of MDF at 7.91 N/mm². If the dowels used in furniture production are subjected to great tensile strength, beech dowels bonded with PVAc adhesive on MDF should be used. However, when dowels produced from MDF and plywood waste are used, they also can produce positive results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 531–535, 2003     

Determination of the optimum conditions for ion nitriding of AISI 5140 steel

AISI 5140 low alloy steel was ion nitrided under different process parameters including time (1, 4, 8 and 12 h), temperature (400, 450, 500 and 550 °C) and gas mixture ratio (0.05, 0.33, 1 and 3 N₂/H₂). By determining the fatigue strength, surface hardness, compound layer thickness and case depth, the optimum working conditions were determined by using a Taguchi design of experiment. After ion nitriding process, it is aimed to maximize fatigue strength, surface hardness and case depth as well as to minimize compound layer thickness. While the optimum conditions were determined, due to the goals (above aims) more than one being, the trade-off among goals was considered. First of all, each goal was optimised, separately. Then, all the goals were optimised together, considering the priority of the goals, and the optimum results were obtained at 0.05 N₂/H₂ gas mixture ratio, at the temperature of 450 °C and for 12 h process time.     

Medical image segmentation with transform and moment based features and incremental supervised neural network

In this study, a novel incremental supervised neural network (ISNN) is proposed for the segmentation of medical images. Performance of the ISNN is investigated for tissue segmentation in medical images obtained from various imaging modalities. Two feature extraction methods based on transform and moments are comparatively investigated to segment the tissues in medical images. Two-dimensional (2D) continuous wavelet transform (CWT) and the moments of the gray-level histogram (MGH) are computed in order to form the feature vectors of ultrasound (US) bladder and phantom images, X-ray computerized tomography (CT) and magnetic resonance (MR) head images. In the 2D-CWT method, feature vectors are formed by the intensity of one pixel of each wavelet-plane of different energy bands. The MGH represents the tissues within the sub-windows by using the spatial variation of image intensities. In this study, the ISNN and Grow and Learn (GAL) network are employed for the segmentation task. It is observed that the ISNN has significantly eliminated the disadvantages of the GAL network in the segmentation of the medical images.     

DESIGN OF TEMPERATURE CONTROLLED QUARTZ CRYSTAL MICROBALANCE SYSTEM

In this study, the dual modulated quartz crystal microbalance (QCM) with heating and cooling control has been developed for the quantitative determination of biological molecules, as a biosensor. On the other hand, since, the Sauerbrey formula is misprinted in some publications, the correct form of formula is also discussed. The proposed QCM biosensor has three main parts, which are the oscillator circuit, temperature control circuit, and the differential frequency measurement unit. Colpitts oscillators with the buffer amplifier, microcontroller (PIC16F877) for the temperature control circuit and a peltier element were used for heating and cooling inside the developed system. Differential frequency measurement is a known technique to compensate environmental effects causing instability of crystals. For this reason, one of the crystals is implemented with oscillatory circuits, i.e., the detector; the other one is used as the reference. The designed system was tested between 8°C and 50°C and frequency shift versus temperature is observed at 0.5 ppm/°C over a given temperature range.     

Evaluation of natural gas hydrates as a future methane source

In recent years, attention has been given to obtaining methane gas from natural gas hydrates (NGHs) sediment; but its production, economics, and safety are still far away from being commercially viable for many years, and so more research is needed. NGHs are nonstoichiometric crystalline solid compounds that form from mixtures of water molecules and light weight natural gases such as methane, ethane, propane, and carbon dioxide. They are formed in specific thermodynamic conditions, low temperatures (5–15°C) and high pressures (2–3 MPa), and are found in (a) onshore polar regions beneath permafrost and (b) offshore deep-sea sediments. Methane, NG, is the cleanest fossil fuel and its huge amounts in NGHs have carbon quantities more than double of all fossil fuels. The methods that have been proposed for NG extraction from NGHs include: (a) depressurization, (b) thermal stimulation, and (c) chemical inhibitor injections. The authors review the potential of methane gas from NGHs as an unconventional source of future energy. The formation of NGHs as well as extraction of methane from NGHs coupled with technical and environmental challenges are also addressed.     

Synthesis of Quaternary,Long-Chain N-Alkyl Amides and Their Corrosion Inhibition in Acidic Media

New cationic surfactants were synthesized by the quaternization of a number of straight-chain amide derivatives with triethylamine or pyridine. The corrosion inhibition tests of the surface-active compounds were performed at room temperature for 24 h on carbon steel coupons in acidic media using the gravimetric method. The acidic media used were 1.5 M HCl and 1.5 M H₂SO₄. Almost all of the synthesized cationic surfactants showed efficient inhibition of corrosion in the test. To establish the inhibition efficiencies of the inhibitors, surface characterization studies (contact angle measurements, SEM analysis and optical profilometer images) of the metal coupons used were performed.